audit: 2026-05-30 full-codebase audit — report, issues, docs, runbooks

Full-codebase-audit 2026-05-30 outputs:
- Audit report: 09 - Audits/Full Codebase Audit - 2026-05-30.md
- 81 issue files ISSUE-055..135 (decisions + 1 skipped no-brainer).
- Scanner docs from scratch (was zero): architecture, data model, API ref, payment
  flow, operations runbook + repo README.
- Doc-sync updates across API reference, data models, flows, design system.
- Secret Rotation Runbook (08 - Operations) for the exposed credentials.
- Reusable workflow guide (07 - Development) + .claude/workflows/full-codebase-audit.js.

Issues remain status:open intentionally — the code fixes are uncommitted-then-committed
working-tree changes per repo and aren't "resolved" until merged/deployed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Issues/ISSUE-098-backend-in-memory-seendeliveryids-resets-on-restart.md

@@ -0,0 +1,38 @@
+---
+issue: 098
+title: "Backend: in-memory seenDeliveryIds resets on restart — webhook dedup lost"
+severity: medium
+domain: Payment
+labels: [bug, backend, idempotency]
+status: open
+created: 2026-05-30
+source: Full Codebase Audit 2026-05-30
+---
+
+# Backend: in-memory seenDeliveryIds resets on restart — webhook dedup lost
+
+**Severity:** medium
+**Domain:** Payment
+**Labels:** bug, backend, idempotency
+
+## Description
+
+`requestNetworkRoutes.ts:16` maintains webhook deduplication via an in-memory `Set` of delivery IDs. This Set is lost on every server restart or pod restart. A redelivered webhook that arrived before the restart will be processed twice, potentially triggering double payment completion.
+
+## Options
+
+1. Persist processed delivery IDs in MongoDB (unique index) with TTL.
+2. Use Redis SET with TTL for delivery-id dedup.
+3. Make webhook handlers idempotent by keying state transitions on payment status guards.
+
+## Recommendation
+
+Persist delivery IDs (Mongo unique index or Redis) AND make handlers idempotent via status guards. This is an infra/state decision.
+
+## Affected Files
+
+- `backend/src/services/payment/requestNetwork/requestNetworkRoutes.ts:16`
+
+## References
+
+- [Full Codebase Audit 2026-05-30](../09%20-%20Audits/Full%20Codebase%20Audit%20-%202026-05-30.md) — DEC-36